1. Field of the Invention
The present invention relates to a workpiece conveying apparatus (workpiece conveying robot) for a pressing machine (press machine).
2. Description of the Related Art
Hitherto, there have been proposed various workpiece conveying apparatus configured to carry workpieces into and out of a press machine, or carry workpieces between the press machines.
In a workpiece conveying apparatus disclosed in Patent Literature 1, attachment parts are arranged at both end portions of a cross bar. For each attachment part, there are arranged a shift driving mechanism and a shift guiding mechanism. The shift driving mechanism is configured to shift the attachment part with respect to the cross bar in a longitudinal direction of the cross bar, that is, in a horizontal direction (lateral direction or Y-axis direction) substantially orthogonal to a workpiece conveying direction. The shift guiding mechanism is configured to guide the shift movement.
The shift driving mechanism disclosed in Patent Literature 1 includes a servomotor. At the time of attachment part replacement or tool replacement, it is necessary to detach a power line, that is, a drive power supply cable, and an encoder line, that is, a control-related cable from a conveying apparatus. Therefore, it is difficult to automatically perform the attachment part replacement, and the attachment part is replaced by manual work. The replacement of the attachment part by manual work takes a very long time, and production is stopped during the replacement. Thus, press production efficiency is lowered.
The attachment part including the servomotor can be automatically removed from the conveying apparatus. However, when the servomotor is removed from the conveying apparatus, position information of the shift driving mechanism is lost. Thus, when the attachment part, that is, the shift driving mechanism is to be mounted to the conveying apparatus again, it is necessary to bring a sensor or the like to a shift reference position on the conveying apparatus to perform an original point setting work. A time period required for the tool replacement can be shortened through automation of the removal work as compared to the case of manual removal work, but the original point setting work is required. Thus, there is a problem in that the total time period for the tool replacement cannot be significantly reduced.
Further, in Patent Literature 2, there is described a workpiece conveying apparatus as illustrated in FIG. 22A. The workpiece conveying apparatus can mutually independently control arm units of two selective compliance assembly robot arm robots (SCARA robots), and distal ends of the arm units of the SCARA robots are coupled to each other by slide arms.
More in detail, in Patent Literature 2, there is described the workpiece conveying apparatus, including:
a first arm unit and a second arm unit, which are rotatably supported by a base arranged at appropriate positions between a press stages and; and
a raising and lowering unit configured to raise and lower both of the arm units,
the first arm unit including a first slide arm,
the second arm unit including a second slide arm,
the first slide arm and the second slide arm being coupled to each other through intermediation of a slide mechanism so as to be slidable to have a variable mutual distance therebetween,
the first slide arm including a first workpiece grasping unit,
the second slide arm including a second workpiece grasping unit,
the first arm unit and the second arm unit being movable independently, and
the workpiece grasping units being adjustable in mutual distance therebetween in accordance with behavior of the arm units.
Herein, Patent Literature 1 corresponds to Japanese Utility Model Application Laid-open No. Hei 04-113126, and Patent Literature 2 corresponds to Japanese Patent No. 5274053.